The present invention relates to a mortar grouting type connector for reinforcing bars, and more particularly to a connector wherein its shell body is provided on the internal surface of the connector with longitudinal flanges for alignment.
Among the different types of connectors for reinforcing bars there is a mortar grouting type connector for reinforcing bars, hereinafter referred to as a splice sleeve, which has been widely used in practice. Typical examples of such connectors are disclosed in U.S. Pat. Nos. 3,540,763 and 4,627,212 which are illustrated in FIG. 6.
The splice sleeve 1 is a longitudinally elongated hollow shell body, both end surfaces thereof being provided with openings and its internal surface being provided with a number of annular ridges 2. The interior of the splice sleeve has a stopper 3 (as disclosed in JP-A-61-233150) which is located approximately at the mid-length portion of the splice sleeve. The side wall has a grouting port 4-a located at a point close to one open end and a discharging port 4-b located at a point close to the other open end. End portions of a pair of reinforcing bars 6-a and 6-b are inserted into this splice sleeve in order to bring their tips into contact with the stopper ridge. Then fluid grouting mortar, hereinafter referred to as grout, is introduced into the splice sleeve. Abutt type connection between the pair of reinforcing bars will be accomplished when the grout has hardened.
The annular ridges 2 are provided so as to enhance the degree of engagement between the internal surface of the splice sleeve and the hardened grout and thereby to increase the interlocking effect of the reinforcing bars in the interior of the splice sleeve. To further enhance this action of increasing the interlocking effect, it is considered desirable that the configuration of the sleeve is such that the diameter of the opening becomes larger and larger from the splice sleeve opening toward the stopper ridge. This action of increasing the interlocking effect caused by the configuration of the sleeve with the diameter of the opening increasing inwardly is called the "wedging action." To obtain such a configuration of the sleeve, two embodiments are possible. One embodiment is an arrangement, as shown in FIG. 6(a), wherein the internal surface of a splice sleeve has a frusto-conical shape, i.e. a shape with the internal diameter progressively increasing from the end opening toward the stopper ridge, and the internal surface is provided thereon with annular ridges of equal height. Another embodiment is an arrangement, as shown in FIG. 6(b), wherein the internal surface of a splice sleeve has a constant diameter of cylindrical shape, i.e. a shape having the same internal diameter throughout its length. The splice sleeve is provided on the internal diameter or surface with annular ridges with their height progressively decreasing from the end opening toward the stopper ridge. The stopper 3 is provided so that the depth of insertion of a reinforcing bar into the splice sleeve can be easily adjusted to a predetermined depth. The grouting port 4-a is used as an inlet opening through which a grout is introduced into the splice sleeve, and the discharging port 4-b is used as an outlet opening for discharging air therethrough upon such grouting.
The splice sleeve exhibits an outstanding advantage over the other types of connectors for reinforcing bars, in particular, when utilized in connection between precast reinforced concrete pillars or wall members, hereinafter referred to as precast vertical members. This will be explained with reference to FIG. 7, which is a view of the upper and lower precast wall members connected together, taken from the members' header side.
A splice sleeve 1 is embedded in the lower end portion of the upper precast reinforced concrete wall member 7-b with its lower opening (i.e. the end opening adjacent to the grouting port) in the latter's lower end surface. The main reinforcing bar 8-b of the member is inserted through the upper opening (i.e. an end opening adjacent to the discharging port) in such a manner that the lower end of the bar comes into contact with the stopper 3. The upper end of the main reinforcing bar 8-b projects a predetermined distance upwardly beyond the upper end surface of the member. The lower precast reinforced concrete wall member 7-a is of the same structure, although the lower end portion thereof does not show another splice sleeve 1 embedded therein. The grouting port 4-a and the discharging port 4-b are connected to pipes for grouting 11-a and 11-b, respectively, with the other ends of the pipes opening to the external surface of the member. The upper precast reinforced concrete wall member is moved down from above the lower precast reinforced concrete wall member set in a vertical position in order to erect the upper member in such a manner that the upwardly projecting upper end of the main reinforcing bar 8-a of the lower member is received by the embedded splice sleeve 1. In the interspace between the upper and lower members, bedding mortar or a beam or floor member (not shown) is placed. Upon the completion of the erection, the upper end tip of the main reinforcing bar 8-a of the lower member is almost in contact with the stopper ridge. Grout (not shown) is then filled through the pipe 11-a into the embedded splice sleeve 1. In the case of connectors for reinforcing bars of types other than the splice sleeve, the longitudinal axes for the pair of reinforcing bars to be connected with each other must be strictly aligned with each other. In the erection of precast vertical members wherein a number of pairs of upper and lower reinforcing bars to be connected with each other between upper and lower members exist, it is impossible for all such bars to be erected in a strictly aligned manner. In contrast, in the case of the splice sleeve, connection is possible even when the pair of upper and lower reinforcing bars are slightly out of alignment as long as the bars can be received into the embedded splice sleeve through its openings. This represents the outstanding advantage of the splice sleeve over other types of connectors for reinforcing bars.
Precast vertical members of the structure as mentioned above may be manufactured as follows. As shown in FIG. 8 illustrating the manufacture of a precast reinforced concrete wall member, a reinforcing bar and sleeve combination with the splice sleeve 1 attached to one end of the reinforcing bar 8, which is to serve as the main reinforcing bar of the member, is arranged horizontally in a mold, and concrete is then placed therein to manufacture the precast reinforced concrete member. In the above-mentioned combination, the tip of the inserted reinforcing bar 8 is in contact with the stopper 3, and the opening through which to insert the reinforcing bar 8 (i.e. the opening adjacent to the discharging port 4-b) and the reinforcing bar 8 are secured together with a rubber plug 12. The end portion of the reinforcing bar 8 constituting one end of the combination passes through the side of the mold 14-a to be supported thereby. The splice sleeve 1 opening at the other end of the combination (i.e. the opening adjacent to the grouting port 4-a) is in contact with and is set to the side of the mold 14-b by means of a sleeve setter 13 as disclosed in U.S. Pat. No. 4,749,170. A special jig for setting the splice sleeve to the mold is located outside the side of the mold (details not shown). Polyvinylchloride pipes 11-a and 11-b are attached to the grouting and discharging ports, respectively, by insertion.
The above-mentioned method of manufacturing precast vertical members having the splice sleeve embedded in the lower end portion has the following problem. The combination of the splice sleeve and the reinforcing bar with the rubber plug 12 lacks rigidity because the plug 12 is made of rubber and is therefore soft. As a consequence, after the reinforcing bar 8 and splice sleeve 1 combination has been placed in the side mold, a phenomenon occurs wherein the combination, due to its own weight, is bent down at the point of the rubber plug securement. This phenomenon is referred to as "displacement of the reinforcing bar." Thus, although the longitudinal axes of the reinforcing bar 8 and the splice sleeve 1 should be in alignment, the displacement of the reinforcing bar 8 causes the axes to cross at an angle which is not desirable.
A splice sleeve provided with an anti-displacement ridge 15 designed to prevent such displacement of the reinforcing bar is disclosed in JP-A-63-7452. This anti-displacement ridge, as shown in FIG. 9, is a ring-formed ridge 15 with a central hole through which the reinforcing bar is to be inserted and is provided on the internal surface of the splice sleeve at a point slightly displaced from the mid-length position. The anti-displacement ridge of the type mentioned above, however, cannot be put to practical use because of the following problems. The first problem is that it hinders the smooth flow of the grout introduced into the splice sleeve from the grouting port to the discharging port. Thus, in order to achieve a sufficient anti-displacement effect, it is necessary for the difference of the diameters between the hole through which the reinforcing bar is to be inserted and the reinforcing bar to be small. In the case of ring-like ridges without notches as shown in FIG. 9(a), however, the cross-sectional area for the passage of the grout is small and also the cross section becomes suddenly throttled. As a result, the smooth flow of the grout is severely hindered, the resistance of the grouting is increased and also a large void is formed adjacent to the ridge. In the case of ring-like ridges with notches as shown in FIG. 9(b), the above-mentioned disadvantage is improved to some extent. However, the ratio of the ring-like ridge's area to the overall cross-sectional area is still high and also the ridge projects like a plate, so that the improvement is small with respect to the elimination of increasing the resistance to grouting and of void formation. The second problem is that the ring-like ridge is easily mistaken for the stopper ridge. Since, as mentioned above, the difference of the diameters is small between the hole in the ring-like ridge through which the reinforcing bar is to be inserted and the reinforcing bar, the tip of the reinforcing bar inserted from the splice sleeve opening does not often pass through the hole but collides with the ring-like ridge. The operator will easily be lead to misunderstand that the collision occurred with respect to the stopper ridge rather than the ring-like ridge. This results in a shorter depth of penetration of the reinforcing bar insertion than should be occurring, thereby decreasing, all the more, the tensile strength of the thus connected reinforcing bars.
The tips of the polyvinylchloride pipes attached by insertion to the grouting and discharging ports must not project into the interior of the splice sleeve. Such a projection will adversely affect the flow of the grout being introduced. However, an undesirable phenomenon often takes place if the polyvinylchloride pipe once set in place is moved, due to its contact with some outside influence in the course of manufacturing the member, into the interior of the splice sleeve with the tip thereof projecting into the interior of the sleeve.